This invention relates to an image forming apparatus and, more particularly, to an improvement in an image forming medium (e.g., paper) feed mechanism in an image forming apparatus such as an electronic copying machine.
In a conventional electronic copying machine, image forming media such as paper sheets are fed one by one by a paper feed mechanism from a paper cassette which acts as a medium storage portion. The sheet is then fed to an image transfer (forming) portion. The paper feed mechanism is arranged such that sheets in the paper cassette are picked up by a paper feed roller as a paper pickup member one by one, and that the sheet is then fed by a pair of aligning rollers as a convey member to the image transfer portion. In some cases, the paper feed roller comprises a semicircular roller.
In the conventional copying machine of this type, when a paper jam or a separation error in the transfer portion occurs, the feed roller is immediately stopped at a current position. After the failure is eliminated, the feed roller returns to the initial position (a noncontact position with respect to the uppermost sheet). Assume that an error occurs while the contact portion of the feed roller is kept in contact with the uppermost sheet in the paper cassette, and that the feed roller is stopped in this state. In this case, it is difficult to remove the detachable feed cassette from the housing of the copying machine. In addition, when paper jam occurs, the jammed sheet cannot be easily removed due to interference of the feed roller. Since the feed roller is rotated and returns to the initial position upon elimination of the failure, the sheet contacting the feed roller is accidentally fed. In this case, even if the copying machine is set in the normal operation mode, the respective mechanism must be operated again to discharge the sheet, resulting in inconvenience.
In a feed mechanism in the conventional electronic copying machine of the type described above, automatic paper feeding for automatically feeding sheets from the paper cassette and manual feeding for manually feeding a sheet from a manual feed guide are selectively performed. This feed mechanism adopts a substantially semicircular feed roller for feeding a sheet in the same manner as described above and a pair of aligning rollers as convey rollers for temporarily stopping the sheet so as to align the sheet and for conveying the sheet to the image transfer portion. Solenoids are connected to the paper feed roller and the pair of aligning rollers, respectively. In this manner, the feed roller and the pair of aligning rollers are separately driven by the corresponding solenoids.
In the conventional feed mechanism, the feed roller and the aligning rollers can be separately controlled by the corresponding solenoids. However, the separate drive mechanisms result in an apparatus of high cost, large dimensions and heavy weight. When a single solenoid is used to control the feed roller and the aligning rollers, only signal control operation is performed for automatic feeding and manual feeding. As a result, proper operations cannot be provided for the different feeding modes, and the sheet cannot be precisely fed.
Thus, it is an object of the present invention to provide a new and improved image forming apparatus which has a storage section for storing an image medium and an image forming section for forming images on the image medium. This image forming apparatus uses a non-circular feed roller to feed the image medium from the storage section to the image forming section. The non-circular feed roller is specially constructed with a curved contact portion and a flat non-contact portion, and the feed roller is disposed so that the curved contact portion contacts the image medium when the contact portion is adjacent to the image medium, thus feeding the image medium towards the image forming section. However, the flat contact portion does not contact the image medium when it is adjacent to the image medium. Therefore, when the flat contact portion is adjacent to the image medium, it poses no obstruction to removal of the storage section and the image medium from the apparatus. The image forming apparatus also has a pair of aligning rollers which aligns the image medium which is fed from the storage section.
This non-circular feed roller and aligning rollers are alternately driven by a drive switching device which has a solenoid and a switching means. This switching means alternately drives the non-circular feed roller when the solenoid is in a first position, or the aligning rollers when the solenoid is in a second position. Thus, the solenoid insures that the feed roller and the aligning rollers cannot be driven simultaneously.
Also, a control means supplies instructions to the apparatus. A first control signal causes the solenoid to assume the first position, and thus feed the image medium to the aligning roller means. A second control signal causes the solenoid to assume the second position, thereby feeding the image medium from the aligning rollers to the image forming section. A third control signal moves the non-circular feed roller so that the non-contact portion is adjacent to the image medium. This third control signal is a jam clearing instruction which facilitates removal of the storage section and the image medium from the apparatus.
It is a further object of the present invention to provide an image medium feeding apparatus which has a storage means for containing the image medium. Feed roller means with a contact surface and a non-contact surface, similarly constructed to that described above, functions to feed the image medium. Shaft means are coupled to the feed roller means, and function to rotate the feed roller. This shaft means is formed with an exterior surface which defines at least two external projections. This shaft means is driven by a drive means. A locking means selectively couples with one of the projections which are formed on the shaft means--by coupling with one projection if necessarily releases another projection. Thus, the shaft means is locked by the locking means at discrete locations and a predetermined amount of rotation between the discreet locations is thereby produced. This amount of rotation corresponds to a feeding operation of the image medium from the storage section.